Hydraulic jack.



K0 MODEL.

w nk leases I I PATENTED APR. 19,,1904. P. H. TILLMAN. HYDRAULIC JACK.

APPLICATION FILED NOV. 8, 1902.

Patented April 19, 1904.

UNITED STATES PATENT OFFICE.

FRANCIS H. STILLMAN, OF NEW YORK, N. Y.

HYDRAULIC JACK.

SPECIFICATION forming part of Letters Patent No. 757,512, dated April 19, 1904. Application and November 3,1902. Serial N0. 130,505. (No model.)

To all whom it may concern:

Be it known that I, FRANCIS H. STILLMAN, a citizen of the United States, and a resident of Brooklyn, in the county of Kings, in the city and State of New York, have invented a certain new and useful Improvement in Hydraulic Jacks, of which the following is a full, clear, and exact description, reference being made to the accompanying drawings, forming part of this specification.

This invention relates to improvements in means to prevent the generation of excessive pressure in hydraulic jacks when heavy objects are quickly lowered with them; and the invention consists of a hydraulic jack having at the top of the fluid-reservoir the capillary vent hereinafter described, and defined in the claims. On the accompanying sheet of drawings,

Figure 1 is a sectional elevation of a fragment of a jack embodying the invention; Fig. 2, a side view of the plug of the charging-orifice,

reservoirs of the most powerful jacks are frac tured by the expansive force of the compressed air, but to obviate this danger by means of a vent through which the fluid would flow if the jack were not upright would be inexpedient for reasons that are apparent.

The object of the invention is to afford the air an exit from the reservoir of such a character as to render it unnecessary to close it to prevent the leakage of fluid from the reservoir through the exit or vent and unnecessary to either regulate it or particularly notice its condition whenever the jack is to be operated.

The jack, of which a fragment is shown in Fig. 1, is of a well-known type, the fluid-reservoir being in the ram and head of the jack. The head 1 is secured on the ram, which is forced upward with the head by pumping fluid into the ram-cylinder under the ram with a pump contained in the jack. The objects raised and lowered with the jack rest on the top 2 of the head or on a claw attached to the head. When the ram is in its lowest position, the surface of the fluid 3 is near the top 2 of the head, as appears by Fig. 1. The

fluid recedes from the top of the head when the ram is raised and approachesit when the ram descends. Hence as the ram descends from its highest position the volume of air between the liquid and top of the head is rendered smaller and smaller until the ram reaches the bottom of the ram-cylinder, when the volume of air is many times smaller than it was at the beginning of the downward movement of the ram. Then if the air cannot escape from the reservoir and a heavy weight has been rapidly lowered with the jack the compression of the air by the action of the Weight on the fluid produces an enormous internal air-pressure, which is liable to fracture the head, as above stated.

The peculiar vent by which the object of the invention is eflected is preferably formed in the plug of the charging-orifice 4, as it is shown herein. It then consists of a slit-or, preferably, a plurality of slits cut in the plug 5, the slit or slits 6 extending into the plug from its exterior and from end to end of the plug, as appears by Figs. 2 and'3. The plug is screw threaded and engages like a common plug with a thread cut in the margin of the chargingorifice 4, in which the plug fits snugly, the slit or slits extending across and inside of the screwthread of the plug. These slits are out with a very thin saw, each being so small that it forms a capillary duct through which air will pass, but through which the fluid used in the jack will not flow. Such a slit differs from any hole that could be drilled through the plug, for it is impracticable, if not impossible, to drill in the plug a hole small enough and long enough to render it capable of performing the functions of one of the slits 6; so while any drilled hole would allow they air to issue from the jack it would not be a capillary duct, but an opening through which the operating fluid of the jack would leak.

A jack provided with the capillary vent described is neither less serviceable nor more troublesome in any respect than a common jack. Although the plug is screwed tightly into the charging-orifice, the vent' satisfaca torily performs its functions. It allows the air to issue from the reservoir rapidly enough to prevent an excessive air-pressure from be ing generated in the jack, and in whatever position the jack may be held the vent does not let any of theliquid escape. The heaviest weight which the jack is capable of raising can be lowered rapidly without subjecting the jack to a greater strain than it is designed to bear with safety. i V v Obviously a slit or slits likeone of the slits 6 and capable of performing like functions might be cut in the margin of the chargingoriflce instead of in the plug;

The benefit derived from this vent is not to be obtained by a loose-fitting plug, because the liquid will leak around such a plug, and besides a loose plug is subject to other objections well known to persons familiar with hydraulic jacks. I

Having-thus described my invention, what I claim as new, and desire to secure by Letters Patent, is

1. A hydraulic jack provided with a capillary vent affording an outlet for the .air that is compressed in the fluid-chamber by the action of a weight rapidly loweredwith the jack.

2. A hydraulic jack provided with a vent comprising a plurality of vC pillary air-ducts affording an outlet for the air that is compressed in the fluid-chamber by the action of a weight rapidly lowered with the jack;

3. A hydraulic jack havinga vent comprising a capillary-air-duct extending through the wall of the fluid-reservoir above the operating fluid, and affording an outlet for the air that is compressed in the fluid-chamber by the action of a weight rapidly lowered with the jack.

i. A hydraulic jack having a vent comprise ing acapillary slit extending through the wall 4 5' of the fluid-reservoir above the operating fluid, and affording an outlet for the air that is compressed in the fluid-chamber by the action of a weight rapidly lowered with the jack.

5. A hydraulic jack having in the wall of the fluid-reservoir above the operating fluid a plug containing a capillary vent extending through the plug and wall, and afiording an outlet for the air that is compressed in the fluid-chamber bythe action of a weight rapidly lowered with the jack.

6. A hydraulic jack having inthe wall of the fluid-reservoir above the operating fluid a plug containing a vent comprising a plurality of capillary aireducts, and affording an outlet forv the air that is compressed in the fluidchamber by the action of a weight rapidly r lowered with the jack. f

'7. A hydraulic jack having "in the wall of the fluid-reservoir above the operating fluid a plug containing a capillary vent comprising a slit cut in the plug and affording an outlet for the air that is compressed in the fluid chamber by the action of a weight rapidly lowered with the jack.

8., A hydraulic jack having in'the chargingorifice a screw-plug slit from end to-end to form in it a capillary vent affording an outlet for the air that is compressed in the fluidchamber by the action of a weight rapidly low- 'ered with the jack. A

9; A hydraulicjack having in the chargingorifice a screw plug slit across the screwthread and from end to end of the plug to form in it a capillary vent affording, an outlet for theair that is compressed in the fluid-chamber by the action of a weight rapidly lowered with the jack FRANCIS H. .STILLMAN.

n presence of- MAUDE E. KIPP, HARRY F. KEILLER. 

